I don't think depression is well enough defined for an unambiguous test to even be possible. Google defines depression as "severe despondency and dejection, ty

I don't think depression is well enough defined for an unambiguous test to even be possible. Google defines depression as "severe despondency and dejection, typically felt over a period of time and accompanied by feelings of hopelessness and inadequacy" which is a reasonable definition, but it really just means "very very sad". When we say someone is suffering from depression does that imply that the cause is medical in nature (not because something horrible happened to them)? How sad does someone have to be before they reach the threshold of depression?